udp.c

   1 /* UDP send/receive module for secnet */
   2
   3 /* This module enables sites to communicate by sending UDP
   4  * packets. When an instance of the module is created we can
   5  * optionally bind to a particular local IP address (not implemented
   6  * yet).
   7  *
   8  * Packets are offered to registered receivers in turn. Once one
   9  * accepts it, it isn't offered to any more. */
  10
  11 #include "secnet.h"
  12 #include <stdio.h>
  13 #include <unistd.h>
  14 #include <fcntl.h>
  15 #include <string.h>
  16 #include <errno.h>
  17 #include <sys/socket.h>
  18 #include <sys/wait.h>
  19 #include <netinet/in.h>
  20 #include <arpa/inet.h>
  21 #include "util.h"
  22 #include "magic.h"
  23 #include "unaligned.h"
  24 #include "ipaddr.h"
  25 #include "magic.h"
  26 #include "comm-common.h"
  27
  28 static comm_sendmsg_fn udp_sendmsg;
  29
  30 struct udp {
  31     struct udpcommon uc;
  32     struct udpsocks socks;
  33 };
  34
  35 /*
  36  * Re comm_addr.ix: This field allows us to note in the comm_addr
  37  * which socket an incoming packet was received on.  This is required
  38  * for conveniently logging the actual source of a packet.  But the ix
  39  * does not formally form part of the address: it is not used when
  40  * sending, nor when comparing two comm_addrs.
  41  *
  42  * The special value -1 means that the comm_addr was constructed by
  43  * another module in secnet (eg the resolver), rather than being a
  44  * description of the source of an incoming packet.
  45  */
  46
  47 static const char *udp_addr_to_string(void *commst, const struct comm_addr *ca)
  48 {
  49     struct udp *st=commst;
  50     struct udpsocks *socks=&st->socks;
  51     static char sbuf[100];
  52     int ix=ca->ix>=0 ? ca->ix : 0;
  53
  54     assert(ix>=0 && ix<socks->n_socks);
  55     snprintf(sbuf, sizeof(sbuf), "udp:%s%s-%s",
  56              iaddr_to_string(&socks->socks[ix].addr),
  57              ca->ix<0 ? "&" : "",
  58              iaddr_to_string(&ca->ia));
  59     return sbuf;
  60 }
  61
  62 static int udp_socks_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  63                                 int *timeout_io)
  64 {
  65     struct udpsocks *socks=state;
  66     int i;
  67     BEFOREPOLL_WANT_FDS(socks->n_socks);
  68     for (i=0; i<socks->n_socks; i++) {
  69         fds[i].fd=socks->socks[i].fd;
  70         fds[i].events=POLLIN;
  71     }
  72     return 0;
  73 }
  74
  75 static void udp_socks_afterpoll(void *state, struct pollfd *fds, int nfds)
  76 {
  77     struct udpsocks *socks=state;
  78     struct udpcommon *uc=socks->uc;
  79     union iaddr from;
  80     socklen_t fromlen;
  81     bool_t done;
  82     int rv;
  83     int i;
  84
  85     struct commcommon *cc=&uc->cc;
  86
  87     for (i=0; i<socks->n_socks; i++) {
  88         struct udpsock *us=&socks->socks[i];
  89         if (i>=nfds) continue;
  90         if (!(fds[i].revents & POLLIN)) continue;
  91         assert(fds[i].fd == us->fd);
  92         int fd=us->fd;
  93         do {
  94             fromlen=sizeof(from);
  95             BUF_ASSERT_FREE(cc->rbuf);
  96             BUF_ALLOC(cc->rbuf,"udp_afterpoll");
  97             buffer_init(cc->rbuf,calculate_max_start_pad());
  98             rv=recvfrom(fd, cc->rbuf->start,
  99                         buf_remaining_space(cc->rbuf),
 100                         0, &from.sa, &fromlen);
 101             if (rv>0) {
 102                 cc->rbuf->size=rv;
 103                 if (uc->use_proxy) {
 104                     /* Check that the packet came from our poxy server;
 105                        we shouldn't be contacted directly by anybody else
 106                        (since they can trivially forge source addresses) */
 107                     if (!iaddr_equal(&from,&uc->proxy)) {
 108                         Message(M_INFO,"udp: received packet that's not "
 109                                 "from the proxy\n");
 110                         BUF_FREE(cc->rbuf);
 111                         continue;
 112                     }
 113                     /* proxy protocol supports ipv4 transport only */
 114                     from.sa.sa_family=AF_INET;
 115                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_addr,4);
 116                     buf_unprepend(cc->rbuf,2);
 117                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_port,2);
 118                 }
 119                 struct comm_addr ca;
 120                 ca.comm=&cc->ops;
 121                 ca.ia=from;
 122                 ca.ix=i;
 123                 done=comm_notify(&cc->notify, cc->rbuf, &ca);
 124                 if (!done) {
 125                     uint32_t msgtype;
 126                     if (cc->rbuf->size>12 /* prevents traffic amplification */
 127                         && ((msgtype=get_uint32(cc->rbuf->start+8))
 128                             != LABEL_NAK)) {
 129                         uint32_t source,dest;
 130                         /* Manufacture and send NAK packet */
 131                         source=get_uint32(cc->rbuf->start); /* Us */
 132                         dest=get_uint32(cc->rbuf->start+4); /* Them */
 133                         send_nak(&ca,source,dest,msgtype,cc->rbuf,"unwanted");
 134                     }
 135                     BUF_FREE(cc->rbuf);
 136                 }
 137                 BUF_ASSERT_FREE(cc->rbuf);
 138             } else { /* rv<=0 */
 139                 BUF_FREE(cc->rbuf);
 140             }
 141         } while (rv>=0);
 142     }
 143 }
 144
 145 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 146                           const struct comm_addr *dest)
 147 {
 148     struct udp *st=commst;
 149     struct udpcommon *uc=&st->uc;
 150     struct udpsocks *socks=&st->socks;
 151     uint8_t *sa;
 152
 153     if (uc->use_proxy) {
 154         struct udpsock *us=&socks->socks[0];
 155         sa=buf_prepend(buf,8);
 156         if (dest->ia.sa.sa_family != AF_INET) {
 157             Message(M_INFO,
 158                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 159                     iaddr_to_string(&dest->ia));
 160             return False;
 161         }
 162         memcpy(sa,&dest->ia.sin.sin_addr,4);
 163         memset(sa+4,0,4);
 164         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 165         sendto(us->fd,sa,buf->size+8,0,&uc->proxy.sa,
 166                iaddr_socklen(&uc->proxy));
 167         buf_unprepend(buf,8);
 168     } else {
 169         int i,r;
 170         bool_t allunsupported=True;
 171         int af=dest->ia.sa.sa_family;
 172         for (i=0; i<socks->n_socks; i++) {
 173             struct udpsock *us=&socks->socks[i];
 174             if (us->addr.sa.sa_family != af)
 175                 /* no point even trying */
 176                 continue;
 177             r=sendto(us->fd, buf->start, buf->size, 0,
 178                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 179             if (r>=0) return True;
 180             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 181                 /* who knows what that error means? */
 182                 allunsupported=False;
 183         }
 184         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 185     }
 186
 187     return True;
 188 }
 189
 190 void udp_destroy_socket(struct udpcommon *uc, struct udpsock *us)
 191 {
 192     if (us->fd>=0) {
 193         close(us->fd);
 194         us->fd=-1;
 195     }
 196 }
 197
 198 bool_t udp_make_socket(struct udpcommon *uc, struct udpsock *us,
 199                        int failmsgclass)
 200 {
 201     const union iaddr *addr=&us->addr;
 202     struct commcommon *cc=&uc->cc;
 203     us->fd=-1;
 204
 205 #define FAIL_LG 0, cc->cl.description, &cc->loc, failmsgclass
 206 #define FAIL(...) do{                                           \
 207         lg_perror(FAIL_LG,errno,__VA_ARGS__);   \
 208         goto failed;                                            \
 209     }while(0)
 210
 211     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 212     if (us->fd<0) FAIL("socket");
 213     setnonblock(us->fd);
 214     setcloexec(us->fd);
 215 #ifdef CONFIG_IPV6
 216     if (addr->sa.sa_family==AF_INET6) {
 217         int r;
 218         int optval=1;
 219         socklen_t optlen=sizeof(optval);
 220         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
 221         if (r) FAIL("setsockopt(,IPV6_V6ONLY,&1,)");
 222     }
 223 #endif
 224
 225     if (uc->authbind) {
 226         pid_t c;
 227         int status;
 228
 229         /* XXX this fork() and waitpid() business needs to be hidden
 230            in some system-specific library functions. */
 231         c=fork();
 232         if (c==-1)
 233             FAIL("fork() for authbind");
 234         if (c==0) {
 235             char *argv[5], addrstr[33], portstr[5];
 236             const char *addrfam;
 237             int port;
 238             afterfork();
 239             switch (addr->sa.sa_family) {
 240             case AF_INET:
 241                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 242                 port=addr->sin.sin_port;
 243                 addrfam=NULL;
 244                 break;
 245 #ifdef CONFIG_IPV6
 246             case AF_INET6: {
 247                 int i;
 248                 for (i=0; i<16; i++)
 249                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 250                 port=addr->sin6.sin6_port;
 251                 addrfam="6";
 252                 break;
 253             }
 254 #endif /*CONFIG_IPV6*/
 255             default:
 256                 fatal("udp (%s:%d): unsupported address family for authbind",
 257                       cc->loc.file,cc->loc.line);
 258             }
 259             sprintf(portstr,"%04X",port);
 260             argv[0]=uc->authbind;
 261             argv[1]=addrstr;
 262             argv[2]=portstr;
 263             argv[3]=(char*)addrfam;
 264             argv[4]=NULL;
 265             dup2(us->fd,0);
 266             execvp(uc->authbind,argv);
 267             _exit(255);
 268         }
 269         while (waitpid(c,&status,0)==-1) {
 270             if (errno==EINTR) continue;
 271             FAIL("waitpid for authbind");
 272         }
 273         if (status) {
 274             if (WIFEXITED(status) && WEXITSTATUS(status)<127) {
 275                 int es=WEXITSTATUS(status);
 276                 lg_perror(FAIL_LG,es,
 277                           "authbind exited with error exit status %d;"
 278                           " indicates error",es);
 279             } else {
 280                 lg_exitstatus(FAIL_LG,status,"authbind");
 281             }
 282             goto failed;
 283         }
 284     } else {
 285         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0)
 286             FAIL("bind (%s)",iaddr_to_string(addr));
 287     }
 288     return True;
 289
 290 failed:
 291     udp_destroy_socket(uc,us);
 292     return False;
 293
 294 #undef FAIL
 295 }
 296
 297 void udp_socks_register(struct udpcommon *uc, struct udpsocks *socks)
 298 {
 299     socks->uc=uc;
 300     socks->interest=
 301         register_for_poll(socks,udp_socks_beforepoll,udp_socks_afterpoll,"udp");
 302 }
 303
 304 void udp_socks_deregister(struct udpcommon *uc, struct udpsocks *socks)
 305 {
 306     socks->uc=uc;
 307     deregister_for_poll(socks->interest);
 308 }
 309
 310 static void udp_phase_hook(void *sst, uint32_t new_phase)
 311 {
 312     struct udp *st=sst;
 313     struct udpsocks *socks=&st->socks;
 314     struct udpcommon *uc=&st->uc;
 315     int i;
 316     for (i=0; i<socks->n_socks; i++)
 317         udp_make_socket(uc,&socks->socks[i],M_FATAL);
 318
 319     udp_socks_register(uc,socks);
 320 }
 321
 322 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 323                          list_t *args)
 324 {
 325     struct udp *st;
 326     list_t *caddrl;
 327     list_t *l;
 328     uint32_t a;
 329     int i;
 330
 331     COMM_APPLY(st,&st->uc.cc,udp_,"udp",loc);
 332     COMM_APPLY_STANDARD(st,&st->uc.cc,"udp",args);
 333     UDP_APPLY_STANDARD(st,&st->uc,"udp");
 334
 335     struct udpcommon *uc=&st->uc;
 336     struct udpsocks *socks=&st->socks;
 337     struct commcommon *cc=&uc->cc;
 338
 339     union iaddr defaultaddrs[] = {
 340 #ifdef CONFIG_IPV6
 341         { .sin6 = { .sin6_family=AF_INET6,
 342                     .sin6_port=htons(uc->port),
 343                     .sin6_addr=IN6ADDR_ANY_INIT } },
 344 #endif
 345         { .sin = { .sin_family=AF_INET,
 346                    .sin_port=htons(uc->port),
 347                    .sin_addr= { .s_addr=INADDR_ANY } } }
 348     };
 349
 350     caddrl=dict_lookup(d,"address");
 351     socks->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
 352     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
 353         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
 354                  UDP_MAX_SOCKETS);
 355
 356     for (i=0; i<socks->n_socks; i++) {
 357         struct udpsock *us=&socks->socks[i];
 358         if (!list_length(caddrl)) {
 359             us->addr=defaultaddrs[i];
 360         } else {
 361             string_item_to_iaddr(list_elem(caddrl,i),uc->port,&us->addr,"udp");
 362         }
 363         us->fd=-1;
 364     }
 365
 366     l=dict_lookup(d,"proxy");
 367     if (l) {
 368         uc->use_proxy=True;
 369         uc->proxy.sa.sa_family=AF_INET;
 370         item=list_elem(l,0);
 371         if (!item || item->type!=t_string) {
 372             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 373         }
 374         a=string_item_to_ipaddr(item,"proxy");
 375         uc->proxy.sin.sin_addr.s_addr=htonl(a);
 376         item=list_elem(l,1);
 377         if (!item || item->type!=t_number) {
 378             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 379         }
 380         uc->proxy.sin.sin_port=htons(item->data.number);
 381     }
 382
 383     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
 384
 385     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 386
 387     return new_closure(&cc->cl);
 388 }
 389
 390 void udp_module(dict_t *dict)
 391 {
 392     add_closure(dict,"udp",udp_apply);
 393 }